This invention relates to a device for detecting and indicating the deviation from a standard, of a timpiece's internal oscillator. It is particularly applicable for use by manufacturers and jewelers who need to determine whether or not a timepiece is operating too fast or too slow so that the timepiece can be properly calibrated. Although calibration instruments have been available before, either the accuracy of the instrument was so poor that it can only be used for rough checking or the expense of the instrument was beyond the means of all but the largest jewelers. This invention is aimed at providing a quality, and accurate calibration instrument which is within the means of the average jeweler. The sensitivity and the signal to noise ratio have been enhanced to a point that the devices are able to measure almost any watch available, and in some cases only contact with the watch bracelet is required.
Prior attempts have been made to develop such a device, typical of these attempts are: patents to Ichikana U.S. Pat. No. 3,946,592, Erickson U.S. Pat. No. 4,024,750, Reese U.S. Pat. No. 3,892,124, Jacker U.S. Pat. No. 3,817,083, Cunitomi U.S. Pat. No. 3,811,315, and Bonny U.S. Pat. No. 3,690,144. Some of these prior devices required cumbersome mechanical clamps or special grounding schemes that had to be applied to the timepiece in order to be measured. Other devices would measure only a particular type of electronic timepiece; such as LED types because of their strong electromagnetic radiation, or stepper motor types because of their detectable ticking sounds. An additional feature of this invention is the device capability of producing a readout in a very short period of time on the order of one second.